It has been proposed to use sintered microporous polymeric materials as the applicator surface for lotion and gel dispensers for more than a decade. However, no products have as yet been marketed using a sintered microporous polymeric material as the applicator surface. There are several reasons. A primary reason is that to date those in the art have been using molded inserts. These are essentially solid pieces with the thinnest part about 0.165 cm or more. These molded inserts are susceptible to breaking upon impact with a solid surface. Also, they deliver product in all directions, including through the edge of the insert.
The inserts are quite fragile since they relatively thin and are made from a sintered porous polymeric material, usually a polyene. As a porous structure is formed in the material the strength of the material decreases. This makes the sintered microporous material susceptible to breaking on impact. Also, due to the random, multidirectional pores, the delivery of a lotion or gel also is from the edges of the applicator surface as well as from the center region. The product that is delivered at the edges generally is not effectively used. In addition it can smear or ooze down the side of the container. This negatively affects the container appearance and can soil the hands of a person using the product.
The latter problem of the delivery of the lotion or gel product flowing from the edges was addressed in European Patent Application 0 775 641 A1. In this patent application a barrier is placed below the insert. The barrier has a central opening so that the only place for flow of product will be through this opening. The lotion or gel then will spread out across the surface. However, there still will be some side surface extrusion. This barrier also will provide some reinforcement to the microporous material.
No publication has addressed the problem of the fragility of the sintered microporous materials. If dispensers are made having these microporous sintered polymeric applicator surfaces, and the dispenser dropped where the microporous sintered polymeric material contacts a hard surface, such as a tile floor, the sintered polymeric material will break. If this application surface breaks, the dispenser is useless. The contained product will flow through the cracks in the surface. It is wasted. However, if the thickness of the sintered porous material is increased to increase strength in an effort to solve this problem, there is an increased cost and an increased resistance to the flow of the lotion or gel through the pores. There is then needed an increased force to dispense that decreases the usefulness of the dispenser. It also deleteriously affects the rheology of the gels and lotions to be dispensed.
There is much prior art directed to the use of these microporous sintered polymeric materials for lotion and gel dispensers. These include U.S. Pat. No. 5,018,894; U.S. Pat. No. 5,073,057, U.S. Pat. No. 5,567,073 and European Patent 0 732 273 B1. Each of these patents discloses the use of Porex.RTM. microporous sintered polymeric materials as an applicator surface. These are described in various shapes and structures. However, they are all directed to the use of molded inserts that are fitted into the top of the applicator surface. They have the above discussed problems. None have disclosed or suggested a solution to these problems.